import Vue from 'vue'

/**
 * @description 自定义指令v-drag
 */
Vue.directive('drag', {
    bind(el, binding, vNode) {
        if (
            el.querySelector('.el-dialog__header') &&
            el.querySelector('.el-dialog')
        ) {
            const dialogHeaderEl = el.querySelector('.el-dialog__header')
            const dragDom = el.querySelector('.el-dialog')
            dialogHeaderEl.style.cssText += ';cursor:move;'
            dragDom.style.cssText += ';top:0;'

            const getStyle = (function () {
                if (window.document.currentStyle) {
                    return (dom, attr) => dom.currentStyle[attr];
                } else {
                    return (dom, attr) => getComputedStyle(dom, null)[attr];
                }
            })();

            dialogHeaderEl.onmousedown = (e) => {
                const disX = e.clientX - dialogHeaderEl.offsetLeft;
                const disY = e.clientY - dialogHeaderEl.offsetTop;

                const dragDomWidth = dragDom.offsetWidth;
                const dragDomHeight = dragDom.offsetHeight;

                const screenWidth = document.body.clientWidth;
                const screenHeight = document.body.clientHeight;

                const minDragDomLeft = dragDom.offsetLeft;
                const maxDragDomLeft = screenWidth - dragDom.offsetLeft - dragDomWidth;

                const minDragDomTop = dragDom.offsetTop;
                const maxDragDomTop = screenHeight - dragDom.offsetTop - dragDomHeight;

                let styL = getStyle(dragDom, 'left');
                let styT = getStyle(dragDom, 'top');

                if (styL.includes('%')) {
                    styL = +document.body.clientWidth * (+styL / 100);
                    styT = +document.body.clientHeight * (+styT / 100);
                } else {
                    styL = +styL.slice(0, -2);
                    styT = +styT.slice(0, -2);
                }

                document.onmousemove = function (event) {
                    let left = event.clientX - disX;
                    let top = event.clientY - disY;

                    if (-left > minDragDomLeft) {
                        left = -minDragDomLeft;
                    } else if (left > maxDragDomLeft) {
                        left = maxDragDomLeft;
                    }

                    if (-top > minDragDomTop) {
                        top = -minDragDomTop;
                    } else if (top > maxDragDomTop) {
                        top = maxDragDomTop;
                    }

                    dragDom.style.cssText += `;left:${left + styL}px;top:${top + styT}px;`;

                    vNode.child.$emit('drag-dialog');
                }

                document.onmouseup = function () {
                    document.onmousemove = null;
                    document.onmouseup = null;
                }
            }
        }
    }
})
